This invention relates to aqueous fuel compositions. Aqueous fuel compositions are desirable for use in internal combustion engines because when combusted they produce reduced nitrogen oxide (NOx) emissions.
One problem with using diesel-fueled engines is to the relatively high flame temperatures reached during combustion. Such high temperatures increase the tendency for the production of nitrogen oxides (NOx). These are formed from both the combination of nitrogen and oxygen in the combustion chamber and from the oxidation of organic nitrogen species in the fuel. Nitrogen oxides comprise a major irritant in smog and are believed to contribute to tropospheric ozone that is a threat to health. Environmental considerations and government regulations have increased the need to reduce NOx production. Various methods for reducing NOx production include use of catalytic converters, engine timing changes, exhaust gas recirculation, and burning of xe2x80x9ccleanxe2x80x9d fuels. These methods are generally too expensive and/or too complicated to be placed in widespread use.
The rates at which Nox are formed is related to the flame temperature. It has been shown that a small reduction in flame temperature can result in a large reduction in the production of nitrogen oxides. One approach to lowering the flame temperature is to inject water in the combustion zone, however; this requires costly and complicated changes in engine design. The latest attempt to use water to reduce flame temperature is the use of aqueous fuels, i.e., incorporating both water and fuel into an emulsion.
Several problems that may occur from long-term use of aqueous fuels include engine corrosion, engine wear, or precipitate deposition which may lead to engine problems and ultimately to inoperability. Problematic precipitate depositions include coalescing ionic species resulting in filter plugging and inorganic post combustion deposits resulting in turbo fouling. Another problem related to aqueous fuel compositions is that they often require substantial engine modifications, such as the addition of in-line homogenizers, thereby limiting any commercial utility. Additionally, many additives used in these fuels, such as silicon produce unwanted engine system deposits.
In addition, such aqueous fuel compositions typically include a lubricity additive designed to reduce the likelihood of scuffing or seizing fuel system components, and in particular the fuel injector plunger. These lubricity additives can be very costly, therefore, any reduction, or total elimination, of the lubricity additive used would reduce the costs of desirable aqueous fuels.
In general, the invention features a substantially ashless fuel composition that includes: (a) hydrocarbon petroleum distillate; (b) purified water; and (c) an additive composition comprising an emulsifier, wherein said additive composition is free from silicon.
The fuel composition preferably is in the form of an aqueous emulsion that is stable at temperatures and pressures encountered during recirculation in a compression ignited engine. The fuel preferably has a pH of at least 9 prior to combustion in the engine thereby inhibiting engine corrosion.
In preferred embodiments, the fuel composition includes a hydrocarbon petroleum distillate, purified water, and an additive composition that includes an emulsifier. The hydrocarbon petroleum distillate is preferably diesel fuel although a naphtha distillate having a boiling point between about 220xc2x0 F. and about 450xc2x0 F. may be used.
The amount of the hydrocarbon petroleum distillate preferably is between about 60 weight percent and about 70 weight percent of the fuel composition, more preferably between about 63 weight percent and about 68 weight percent of the fuel composition.
The purified water preferably contains no greater than about 50 parts per million calcium and magnesium ions, and no greater than about 20 parts per million silicon. More preferably, the purified water contains no greater than about 2 parts per million calcium and magnesium ions, and preferably no silicon but no greater than about 1 part per million silicon. The amount of purified water preferably is between about 28 weight percent and about 40 weight percent of the fuel composition, more preferably between about 30 weight percent and about 35 weight percent of the fuel composition.
In a particularly preferred composition, the amount of the petroleum distillate ranges from about 43 weight percent to about 70 weight percent, the amount of the purified water ranges from about 28 weight percent to about 40 weight percent, and the amount of the additive composition is no greater than about 10 weight percent.
Many compounds which would otherwise be useful as components of the additive composition contain trace amounts of silicon and are not desirable. These silicon additives produce exhaust system deposits that are an indication of high particulate emissions that can result in premature failure of combustion chamber and exhaust system components.
The emulsifier preferably is selected from the group consisting of nonionic, anionic, and amphoteric emulsifiers, and combinations thereof. An example of a preferred alkyl amphoteric emulsifier is one having at least 12 carbon atoms. The amount of the alkyl amphoteric emulsifier preferably is between about 0.01 weight percent and about 0.1 weight percent of the fuel composition.
In additional preferred embodiments, the additive composition includes an alllylphenolethoxylate (e.g., a polyethoxylated nonylphenol having between about 8 and 12 moles of ethylene oxide per mole of nonylphenol, more preferably about 9 moles of ethylene oxide per mole of nonylphenol), an alcohol ethoxylate, a fatty alcohol ethoxylate, an alkyl amine ethoxylate, or a combination thereof. In the case of alkylphenolethoxylates, the ingredient preferably is present in an amount ranging from about 0.04 weight percent to about 1.0 weight percent of the fuel composition.
The additive composition preferably includes an organophosphoric or carboxylic mono-, di-, or tri-functional acid having at least 12 carbon atoms. An example of a preferred acid is selected from the group consisting of di- and tri-acids of the Diels-Alder adducts of unsaturated fatty acids (preferably having between about 12 and about 22 carbon atoms) and mixtures thereof. For example, the acid may be a C21 dicarboxylic acid derived from the Diels-Alder adduct of maleic anhydride and oleic acid. The amount of the mono-, di-, or tri-acid preferably is between about 0.04 weight percent and about 0.1 weight percent of the fuel composition, more preferably between about 0.04 weight percent and about 0.05 weight percent of the fuel composition.
The additive composition preferably includes an alkanolamine. Examples of preferred alkanolamines include those selected from the group consisting of amino methyl propanol, triethanolamine,. diethanolamine, and combinations thereof, with amino methyl propanol being preferred. The amount of the alkanolamine preferably is between about 0.05 weight percent and about 0.4 weight percent of the fuel composition, more preferably about 0.06 weight percent of the fuel composition.
The additive composition preferably includes an aminoalkanoic acid. An example of a preferred aminoalkanoic acid is available from the Keil Chemical Division of Ferro Corporation under the trade designation xe2x80x9cSynkad 8281xe2x80x9d. The amount of the aminoalkanoic acid preferably is between about 0.03 weight percent and 0.15 weight percent, more preferably 0.03 about 0.05 weight percent.
In some preferred embodiments, the additive composition includes antifreeze. The amount of antifreeze preferably is between about 2 weight percent and about 9 weight percent of the fuel composition. Examples of preferred antifreezes include C1 to C3 alcohols, e.g., methanol, ethanol and isopropanol.
In some preferred embodiments, the additive composition includes an ignition delay modifier. Preferred ignition delay modifiers include those selected from the group consisting of nitrates, nitrites, peroxides, and combinations thereof. An example of a preferred ignition delay modifier is 2-ethyihexylnitrate. The amount of the ignition delay modifier preferably is between about 0.1 weight percent and about 0.4 weight percent of the fuel composition.
The components of the fuel composition, and the relative amounts thereof, are preferably selected such that the fuel composition is suitable for use in diesel engines. This includes varying the formula of the fuel to maintain the lower heating value of the fuel within a range for which the engine fuel system is designed. Additionally, the fuel composition is preferably ashless, is preferably is stable at temperatures and pressures encountered during recirculation in a compression ignited engine and has a pH of at least 9 prior to combustion to inhibit engine corrosion.
Preferably the amount of the petroleum distillate ranges from about 60 weight % to about 70 weight %, the amount of the purified water ranges from about 28 weight % to about 40 weight %, and the amount of the additive composition is no greater than about 10 weight % of the fuel composition.
The fuel composition preferably has a pH of at least about 9 prior to combustion ion the engine to inhibit engine corrosion, Moreover, the fuel composition preferably is stable at temperatures and pressures encountered during recirculation in a compression ignited engine.
In a second aspect of the invention, the invention features a fuel composition that includes: (a) a hydrocarbon petroleum distillate; (b) purified water; (c) methanol; (d) polyethoxylated nonylphenol, having about 9 moles of ethylene oxide per mole of nonylphenol; (e) C21 dicarboxylic acid derived from the Diels-Alder adduct of maleic anhydride and oleic acid; (f) amino methyl propanol; (g) an aminoalkanoic acid; and (h) 2-ethylhexyl nitrate.
The invention provides improved fuel compositions that are stable for extended periods of time under conditions typically encountered during storage. In addition, the fuels burn cleanly and efficiently.
In yet another embodiment of the invention, the amount of any lubricity additive can be reduced or eliminated by providing a protective coating to selected fuel system components, including the fuel injector plunger. The preferred fuel injector plunger coating is a metal nitride.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.